1. Homework Answers 1. 4.17 m/s 2. 22.36 m2 3. 13.5 g/L 4. 5712 cm3
5. 60 kg·m/s
N·m/s
kg/cm2
mm3
kg·m/s2
N·m
J/g·oC
J/g
mol/L
15. y/2
17. 3d3

2. More answers…
18. X=11.5
22. X=3.5
23. X=2
24. X= H/WQ
25. X= T+6/Y
26. X=23FG-8
27. X=EF2/18KR
28. X=T/LS
29. X= -w+15G
30. X= T3KE4R/B2H5Y
x105
x10-6
x107

3. x1027
,000
x10-7
x10-15
x102
x104
x10-15
x10-3
x1012

4. Scientific Measurement
MAKE SURE YOU HAVE A CALCULATOR!!
Scientific Measurement

5. Units of Measurement
SI Units
System used by scientists worldwide

6. Prefixes used with SI units

7. 1,000
100
kilo k 10
hecto h 1
deca dc
0.1
Meter
Liter
Gram
Staircase Rule:
The direction you slide your finger is the direction the decimal place goes!
0.01
deci d
0.001
centi c
milli m

8. Derived Units A unit that is defined by a combination of base units
Volume
Density

9. Density A ratio that compares the mass of an object to its volume
The units for density are often g/cm3
Formula:

10. Example Problem
Suppose a sample of aluminum is placed in a 25-mL graduated cylinder containing 10.5mL of water. The level of the water rises to 13.5mL. What is the mass of the sample of aluminum?
Volume: final-initial13.5mL-10.5mL= 3.0mL
Density: 2.7 g/mL (Appendix C)
Mass: ????

12. Temperature Kelvin is the SI base unit for temperature
Water freezes at about 273K
Water boils at about 373K
Conversion: 0C +273 =Kelvin

14. Using and Expressing Measurements
A measurement is a quantity that has both a number and a unit.
Measurements are fundamental to the experimental sciences. For that reason, it is important to be able to make measurements and to decide whether a measurement is correct.

15. Dimensional Analysis *Very Important*
A method of problem solving that focuses on the units to describe matter
Conversion factor- a ratio of equivalent values used to express the same quantity in different units
Example: 9.00 inches to centimeters
Conversion factor: 1 in = 2.54 cm

16. Scientific notation
We often use very small and very large numbers in chemistry. Scientific notation is a method to express these numbers in a manageable fashion.
Definition: Numbers are written in the form M x 10n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number.
= 5 x 103
= 5 x (10 x 10 x 10)
= 5 x 1000 =
Numbers > one have a positive exponent.
Numbers < one have a negative exponent.

17. Example
Ex. 602,000,000,000,000,000,000,000 
Ex 
In scientific notation, a number is separated into two parts.
The first part is a number between 1 and 10.
The second part is a power of ten.
6.02 x1023
1.775 x10-3

18. Examples
730,000
122,091

19. ANSWERS
 9.13x10-4
730,000 7.3x105
122,091 x105
 1.24x10-3 

20. Accuracy and precision
Your success in the chemistry lab and in many of your daily activities depends on your ability to make reliable measurements. Ideally, measurements should be both correct and reproducible.
Accuracy: a measure of how close a measurement comes to the actual or true (accepted) value of whatever is being measured.
Precision: a measure of how close a series of measurements are to one another

21. Good Accuracy
Poor Precision
Poor Accuracy
Poor Precision
Poor Accuracy
Good Precision
Good Accuracy
Good Precision

22. Determining error Error
- the difference between the accepted value and the experimental value
Accepted Value: referenced/true value
Experimental Value: value of a substance's properties found in a lab.

23. Example
A student takes an object with an accepted mass of 150 grams and masses it on his own balance. He records the mass of the object as 143 grams. What is his percent error?

24. % ERROR Accepted value: 150 grams Experimental value: 143 grams
Error= 150grams – 143 grams = 7 grams
% ERROR

25. Significant Figures
The significant figures in a measurement include all of the digits that are known, plus the last digit that is estimated.
Measurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures in the values used in the calculation.
Instruments differ in the number of significant figures that can be obtained from their use and thus in the precision of measurements.

26. Rules for Determining Sig Fig’s
Every nonzero digit in a reported measurement is assumed to be significant.
The measurements 24.7 meters, meter, and 714 meters each express a measure of length to 3 significant figures.
Zeros appearing between nonzero digits are significant.
The measurements 7003 meters, meters, and meters each have 4 significant figures.

27. 3. Leftmost zeros appearing in front of nonzero digits are NOT significant. They act as placeholders.
The measurements meter, and 0.42 and meter each have only 2 significant figures.
By writing the measurements in scientific notations, you can eliminate such place holding zeros: in this case 7.1 x10-3 meter, 4.2x10-1 meter, and 9.9x10-5 meter.

28. 4. Zeros at the end of a number to the right of a decimal point are always significant.
The measurements meters, meters, and meters each have 4 significant figures.
5. Zeros at the rightmost end of a measurement that lie to the end of an understood decimal point are NOT significant if they serve as placeholders to show the magnitude of the
The zeros in the measurements 300 meters, 7000 meters, and 27,210 meters are NOT significant.

29. 6. There are two situations in which numbers have unlimited number of significant figures.
The first involves counting. If you count 23 people in the classroom, then there are exactly 23 people, and this value has an unlimited number of significant figures.
The second situation involves exactly defined quantities such as those found within a system of measurement. For example, 60 min= 1 hour, each of these numbers have unlimited significant figures.

30. ABSENT DECIMAL
Atlantic Ocean
PRESENT DECIMAL
Pacific Ocean

31. EXAMPLES 123 m: 9.8000 x104m: 0.07080 m: 40,506 mm: 22 meter sticks:

32. ANSWERS
123 m: 3
x104m: 5
m: 4
40,506 mm: 5
22 meter sticks: unlimited
98,000 m: 2

33. Rounding Rules: Addition/Subtraction
When you add/subtract measurements, your answer must have the same number of digits to the RIGHT of the decimal point as the value with the FEWEST digits to the right of the decimal point
Example: cm cm cm cm
Rounded to cm
Fewest Decimal places

34. Rounding Rules: Multiplication/Division
When you multiply or divide numbers, your answer must have the same number of significant figures as the measurements with the FEWEST significant figures
Example: 3.20cm x 3.65cm x 2.05cm=
= cm3
Rounded = 23.9 cm3
Each has 3 sig fig’s

35.  HOMEWORK  Finish #2 and #3 from previous worksheet Page 29 #1-3,
Pages #14-16
Page 38 #29-30
Pages #31-38